The Supreme Court on Tuesday began hearing arguments in a case that could rewrite the rule book for Fox, ABC and other broadcast stations now prohibited from pushing nudity and profanity on the public airwaves.

In an unlikely alliance, the Obama administration has partnered with the Family Research Council, Morality in Media and other socially conservative groups in arguing that network television should remain a “safe harbor” for children and families, where one need not fear “wardrobe malfunctions” during the Super Bowl or dirty words during the Billboard Music Awards.

But the entertainment industry’s heavy hitters, led by Fox, have mounted a First Amendment case and reject the notion that, in the age of unregulated cable channels and countless raunchy websites just a click away, the Federal Communications Commission has to play the role of moral gatekeeper for American families.

A ruling is expected this summer. If the justices declare current FCC regulations unconstitutional, the R-rated effects eventually will be seen from the living room couch.

“I don’t think things would change overnight, but I do think it would change. Slowly, more and more profanity and nudity would start to creep into much of the programming,” said Susan Low Bloch, a law professor at Georgetown University.

Networks’ decision-making, Ms. Bloch said, “will be a dollar calculation, not a moral calculation,” and television executives could bet that more sex, violence and four-letter words will equal bigger profits.

Obama administration attorneys and others argue that the media world of the 21st century is polluted with enough filth, and giving broadcasters carte blanche to do as they please will mean the death knell for family-friendly programming.

“This is about letting children be children,” said Ken Klukowski, director of the Center for Religious Liberty at the Family Research Council. “The First Amendment is not a license for an adult to say or do anything they want, anytime they want, in the presence of children. If you have 800 channels out there that you can put your content on, what’s the big deal about having four or five” stations free of objectionable material?

Chief Justice John G. Roberts Jr. seems to agree. At Tuesday’s hearing, Chief Justice Roberts, the only member of the court with young children, said there are hundreds of cable channels not bound by any FCC restrictions, and that should be enough for people who want racier fare.

“All we are asking for, what the government is asking for, is a few channels where … they are not going to hear the S-word, the F-word, they are not going to see nudity,” the chief justice said.

The broad question of how far networks’ free-speech rights extend may not be resolved with this case, and the court could choose to limit its ruling to the FCC’s current indecency enforcement policy, which was declared unconstitutional by the 2nd U.S. Circuit Court of Appeals two years ago.

Fox violated that policy several times in the past decade, including a 2002 incident in which the entertainer Cher uttered the F-word during the 2002 Billboard Music Awards. Reality star Nicole Richie followed suit in 2003, using the same expletive during a live appearance on the program.

Other networks also have been targeted. ABC stations were hit with fines after an episode of “NYPD Blue” featured a lengthy shot of a woman’s naked buttocks. The nudity was shown before 10 p.m. Eastern, the traditional cut-off point for indecent material.

ABC spokeswoman Julie Hoover said Tuesday that the network maintains the nudity on “NYPD Blue” was “not indecent,” and the fines were “unwarranted and unconstitutional.”

“We believe that the decision by the U.S. Court of Appeals was correct and should be affirmed by the Supreme Court,” she said.

ABC and other networks have long questioned the consistency of the FCC rule, since it seems to be randomly enforced.

Such strong adult fare as Steven Spielberg’s “Saving Private Ryan” and “Schindler’s List” have been shown on prime-time network television unedited. Six months after the Sept. 11, 2001, terrorist attacks, CBS aired the documentary “9/11,” which followed a firefighting crew coincidentally being videotaped that day and accordingly contained multiple spontaneous F-words and other profanities. No fines were issued.

The apparent hypocrisy wasn’t lost on Justice Elena Kagan, who joked Tuesday that the FCC policy is “Nobody can use dirty words or nudity, except Steven Spielberg.”

But it won’t be individual incidents that ultimately sway the justices. Indeed, Justice Samuel Anthony Alito Jr. said Tuesday that technological advances may make current FCC rules obsolete, since nearly 90 percent of households now have cable or satellite television, enabling them to easily surf between regulated network stations and unregulated cable channels.

“I’m sure your clients will continue to make billions of dollars on their programs which are transmitted by cable and by satellite and by Internet,” he told the lawyers representing the TV networks. “But to the extent they are making money from people who are using rabbit ears, that is disappearing.”

Nathan Siegel, a First Amendment lawyer and law professor at the University of Maryland, said the initial rationale for FCC regulation was that the airwaves are public property and needed to be regulated as a public utility.

“These are not new questions. The reason the courts have [in the past] decided it’s OK to continue government regulations was because there were really no other alternatives for people to watch at the time. Those realities … don’t exist anymore,” he said.

Mr. Siegel also said that, such legal rationales aside, regulating such a small segment of TV offerings, as Chief Justice Roberts and social conservatives note when they argue that the restrictions are not onerous, is simply irrational.

“There are multiple ways that people can get content. Does it make any sense to give the FCC the exclusive power to regulate only broadcast programming when nothing else is regulated?” he asked.